Endothelial Cell CD36 Regulates Membrane Ceramide Formation, Exosome Fatty Acid Delivery to Tissues and Circulating Fatty Acid Levels

Endothelial cell (EC) CD36 controls tissue fatty acid (FA) uptake. Here we examined how ECs transfer FAs. FA interaction with apical membrane CD36 induced Src phosphorylation of caveolin-1 tyrosine-14 (Cav-1Y14) and ceramide generation in caveolae. Fission of the caveolae yielded vesicles containing FAs, CD36 and ceramide that were secreted basolaterally as small (80-100nm) exosome-like extracellular vesicles (sEVs). We visualized EC transfer of FAs in sEVs to underlying myotubes in transwells. In mice with EC-expression of the exosome marker emeraldGFP-CD63, muscle fibers accumulated circulating FAs in emGFP-labeled puncta. The FA-sEV pathway was mapped through its suppression by CD36 depletion, blocking actin-remodeling, Src inhibition, Cav-1Y14 mutation, and neutral sphingomyelinase 2 inhibition. Suppression of sEV formation in mice reduced muscle FA uptake, raised circulating FAs, which remained in blood vessels, and lowered glucose, mimicking prominent Cd36-/- phenotypes. The findings show that FA uptake influences membrane ceramide, endocytosis, and EC communication with parenchymal cells. Gene expression analyses was conducted using RNASeq on control or CD36 knockdown human dermal microvascular cells